People are generally aware of the most common causes of hallucinations, like schizophrenia and a really high fever. But lesser known are the more rare causes; here are six you probably haven't heard about.

Key to Adult Happiness: Be Popular, Not Smart, in School

More research shows that high school is the most important time of your life. This time research shows that friends, not intelligence was crucial to future well-being. New research indicates that it is not intelligence that determines adult well-being – but the quality of friendships made during adolescence and childhood.

Researchers in New Zealand enrolled 1,037 children in their longitudinal study. The children were assessed at three years old, and then reassessed around their birthdays at age five, seven, nine, 11, 13, 15, 18, 21, 26, 32, and most recently at age 38. At age 38, 964 participants were interviewed, representing 95 percent of the 1,015 participants who were still alive. Craig Olsson and his team said, "Compared with the social connectedness pathway, the direct effect of adolescent academic achievement on adult well-being was smaller."

Participants were questioned on various measures, with researchers focusing on family disadvantage, social connectedness, language development in childhood, and academic achievement in high school. Family disadvantage was measured through "socioeconomic status, family climate of mental health, and parent–child interaction practices."

Social connectedness was measured by "peer social inclusiveness [and] cooperative playing with other children, level of conﬁdence, conversing with others, and sharing with others" during childhood and "quality of social attachments, participation in [organized] clubs and groups, self-perceived competencies or strengths, and life satisfaction between 15 and 18 years." Language development was measured through speaking ability and reading ability. Academic achievement was measured with grades and with an attachment to school. Adult well-being was measured through "four constructs: sense of coherence, positive coping styles, social participation, and [pro-social] behavior."

It may sound surprising that intelligence and family disadvantage played less of a role in adult well-being than social-connectedness, and perhaps it is. We all know someone who was a bit awkward in high school and is now doing really well for himself or herself but psychologists were looking not at financial stability or wealth, but happiness – and, as so many have said, money cannot buy happiness.

Researchers acknowledge that academic success and social rank often have little to do with one another, and note that "[if] social and academic pathways are separate, then, positive social development across childhood and adolescence requires investments beyond development of the academic curriculum."

So science has confirmed what people have been saying for years: "It's not about what you know, but who you know."